There are some hints in https://wiki.openstack.org/wiki/Documentation/HypervisorTuningGuide There are some tips in https://www.linux-kvm.org/page/Tuning_KVM too but you’d need to find the corresponding OpenStack flags on the guest/images/hosts/flavors. Overall, there are several options so it’s recommended to establish a baseline performance on a representative work load and try the various options. Tim From: Manuel Sopena Ballesteros <manuel.sb@garvan.org.au> Date: Wednesday, 1 May 2019 at 06:35 To: "openstack-discuss@lists.openstack.org" <openstack-discuss@lists.openstack.org> Subject: how to get best io performance from my block devices Dear Openstack community, I would like to have a high performance distributed database running in Openstack vms. I tried attaching dedicated nvme pci devices to the vm but the performance is not as good as I can get from bare metal. Bare metal: [root@zeus-54 data]# fio --ioengine=libaio --name=test --filename=test --bs=4k --size=40G --readwrite=randrw --runtime=120 --time_based test: (g=0): rw=randrw, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=libaio, iodepth=1 fio-3.1 Starting 1 process Jobs: 1 (f=1): [f(1)][100.0%][r=39.5MiB/s,w=39.6MiB/s][r=10.1k,w=10.1k IOPS][eta 00m:00s] test: (groupid=0, jobs=1): err= 0: pid=50892: Wed May 1 22:22:45 2019 read: IOPS=9805, BW=38.3MiB/s (40.2MB/s)(4596MiB/120001msec) slat (usec): min=39, max=6678, avg=94.72, stdev=55.78 clat (nsec): min=450, max=18224, avg=525.83, stdev=120.10 lat (usec): min=39, max=6679, avg=95.36, stdev=55.79 clat percentiles (nsec): | 1.00th=[ 462], 5.00th=[ 478], 10.00th=[ 482], 20.00th=[ 486], | 30.00th=[ 490], 40.00th=[ 494], 50.00th=[ 502], 60.00th=[ 510], | 70.00th=[ 516], 80.00th=[ 532], 90.00th=[ 596], 95.00th=[ 676], | 99.00th=[ 860], 99.50th=[ 1048], 99.90th=[ 1384], 99.95th=[ 2480], | 99.99th=[ 3728] bw ( KiB/s): min= 720, max=40736, per=100.00%, avg=39389.00, stdev=5317.58, samples=239 iops : min= 180, max=10184, avg=9847.23, stdev=1329.39, samples=239 write: IOPS=9799, BW=38.3MiB/s (40.1MB/s)(4594MiB/120001msec) slat (nsec): min=2982, max=106207, avg=4220.09, stdev=980.04 clat (nsec): min=407, max=18130, avg=451.48, stdev=103.71 lat (usec): min=3, max=111, avg= 4.74, stdev= 1.03 clat percentiles (nsec): | 1.00th=[ 414], 5.00th=[ 418], 10.00th=[ 422], 20.00th=[ 430], | 30.00th=[ 434], 40.00th=[ 434], 50.00th=[ 438], 60.00th=[ 438], | 70.00th=[ 442], 80.00th=[ 446], 90.00th=[ 462], 95.00th=[ 588], | 99.00th=[ 700], 99.50th=[ 916], 99.90th=[ 1208], 99.95th=[ 1288], | 99.99th=[ 3536] bw ( KiB/s): min= 752, max=42608, per=100.00%, avg=39366.63, stdev=5355.73, samples=239 iops : min= 188, max=10652, avg=9841.64, stdev=1338.93, samples=239 lat (nsec) : 500=69.98%, 750=28.64%, 1000=0.90% lat (usec) : 2=0.42%, 4=0.04%, 10=0.01%, 20=0.01% cpu : usr=2.20%, sys=10.85%, ctx=1176675, majf=0, minf=1372 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% issued rwt: total=1176625,1175958,0, short=0,0,0, dropped=0,0,0 latency : target=0, window=0, percentile=100.00%, depth=1 Run status group 0 (all jobs): READ: bw=38.3MiB/s (40.2MB/s), 38.3MiB/s-38.3MiB/s (40.2MB/s-40.2MB/s), io=4596MiB (4819MB), run=120001-120001msec WRITE: bw=38.3MiB/s (40.1MB/s), 38.3MiB/s-38.3MiB/s (40.1MB/s-40.1MB/s), io=4594MiB (4817MB), run=120001-120001msec Disk stats (read/write): nvme9n1: ios=1174695/883620, merge=0/0, ticks=105502/72225, in_queue=192101, util=99.28% From vm: [centos@kudu-1 nvme0]$ sudo fio --ioengine=libaio --name=test --filename=test --bs=4k --size=40G --readwrite=randrw --runtime=120 --time_based test: (g=0): rw=randrw, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=libaio, iodepth=1 fio-3.1 Starting 1 process Jobs: 1 (f=1): [m(1)][100.0%][r=29.2MiB/s,w=29.7MiB/s][r=7487,w=7595 IOPS][eta 00m:00s] test: (groupid=0, jobs=1): err= 0: pid=44383: Wed May 1 12:22:24 2019 read: IOPS=6994, BW=27.3MiB/s (28.6MB/s)(3278MiB/120000msec) slat (usec): min=54, max=20476, avg=115.27, stdev=71.45 clat (nsec): min=1757, max=31476, avg=2163.02, stdev=688.66 lat (usec): min=56, max=20481, avg=118.51, stdev=71.66 clat percentiles (nsec): | 1.00th=[ 1800], 5.00th=[ 1832], 10.00th=[ 1864], 20.00th=[ 1992], | 30.00th=[ 2040], 40.00th=[ 2064], 50.00th=[ 2064], 60.00th=[ 2096], | 70.00th=[ 2096], 80.00th=[ 2128], 90.00th=[ 2480], 95.00th=[ 2544], | 99.00th=[ 4448], 99.50th=[ 5536], 99.90th=[11072], 99.95th=[12736], | 99.99th=[18560] bw ( KiB/s): min= 952, max=31224, per=100.00%, avg=28153.51, stdev=4126.89, samples=237 iops : min= 238, max= 7806, avg=7038.23, stdev=1031.70, samples=237 write: IOPS=6985, BW=27.3MiB/s (28.6MB/s)(3274MiB/120000msec) slat (usec): min=7, max=963, avg=12.60, stdev= 6.24 clat (nsec): min=1662, max=199250, avg=2030.26, stdev=712.33 lat (usec): min=10, max=970, avg=15.68, stdev= 6.48 clat percentiles (nsec): | 1.00th=[ 1688], 5.00th=[ 1720], 10.00th=[ 1736], 20.00th=[ 1864], | 30.00th=[ 1928], 40.00th=[ 1944], 50.00th=[ 1944], 60.00th=[ 1960], | 70.00th=[ 1960], 80.00th=[ 1992], 90.00th=[ 2352], 95.00th=[ 2384], | 99.00th=[ 4048], 99.50th=[ 4768], 99.90th=[11456], 99.95th=[13120], | 99.99th=[19072] bw ( KiB/s): min= 912, max=31880, per=100.00%, avg=28119.64, stdev=4176.38, samples=237 iops : min= 228, max= 7970, avg=7029.75, stdev=1044.07, samples=237 lat (usec) : 2=51.56%, 4=47.17%, 10=1.03%, 20=0.22%, 50=0.01% lat (usec) : 250=0.01% cpu : usr=4.96%, sys=28.37%, ctx=839307, majf=0, minf=26 IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% issued rwt: total=839283,838268,0, short=0,0,0, dropped=0,0,0 latency : target=0, window=0, percentile=100.00%, depth=1 Run status group 0 (all jobs): READ: bw=27.3MiB/s (28.6MB/s), 27.3MiB/s-27.3MiB/s (28.6MB/s-28.6MB/s), io=3278MiB (3438MB), run=120000-120000msec WRITE: bw=27.3MiB/s (28.6MB/s), 27.3MiB/s-27.3MiB/s (28.6MB/s-28.6MB/s), io=3274MiB (3434MB), run=120000-120000msec Disk stats (read/write): nvme0n1: ios=838322/651596, merge=0/0, ticks=83804/22119, in_queue=104773, util=70.18% Is there a way I can get near bare metal performance from my nvme block devices? NOTICE Please consider the environment before printing this email. This message and any attachments are intended for the addressee named and may contain legally privileged/confidential/copyright information. If you are not the intended recipient, you should not read, use, disclose, copy or distribute this communication. If you have received this message in error please notify us at once by return email and then delete both messages. We accept no liability for the distribution of viruses or similar in electronic communications. This notice should not be removed.